Centre Header Image

Hello, I would like to center the Header Image and have gone through your forums but cannot get it right. Are you able to assist. I tried copying in the following code within the Custom CSS section, without success: #site-logo, hgroup.with-logo { clear: none; display: inline; float: centre; } My site is http://www.grahamgouldmotors.com.au I have managed to find a way since but not sure if it is centred correctly. Also, is there a way to change the colour around the image. Sorry one more thing centering the header text as well. Thanks, Regards, Anthony